Code samples

Introduction

A ground overlay is an image that is fixed to a map. Unlike markers, ground
overlays are oriented against the Earth's surface rather than the screen, so
rotating, tilting or zooming the map will change the orientation of the image.
Ground overlays are useful when you wish to fix a single image at one area on
the map. If you want to add extensive imagery that covers a large portion of the
map, you should consider a Tile overlay.

Add an overlay

To add a GroundOverlay, create a
GroundOverlayOptions object that defines both an
image and a position. You can optionally specify additional settings that will
affect the positioning of the image on the map. Once you've defined the
necessary options, pass the object to the GoogleMap.addGroundOverlay()
method to add the image to the map. The addGroundOverlay() method returns a
GroundOverlay object; you should retain a reference to
this object if you want to modify it later.

Note: When the image is added to the map it will be converted to an image with
sides that are powers of two. You can avoid this conversion by using an
original image with dimensions that are powers of two — for example,
128x512 or 1024x1024.

Step by step:

Instantiate a new GroundOverlayOptions object

Specify the image as a BitmapDescriptor.

Set the position of the image using one of the available methods:

position(LatLng location, float width, float height)

position(LatLng location, float width)

positionFromBounds(LatLngBounds bounds)

Set any optional properties, such as transparency, as desired.

Call GoogleMap.addGroundOverlay() to add the image to the map.

The below example demonstrates how to add a ground overlay to an existing
GoogleMap object.

If you wish to change or remove a ground overlay after you've added it to
the map, ensure that you keep hold of the GroundOverlay object. You can
modify the overlay later by making changes to this object.

Remove an overlay

Change an overlay

You can change the ground overlay image after it's been added to the map with
the GroundOverlay.setImage(BitmapDescriptor) method.

// Add an overlay, retaining a handle to the GroundOverlay object.
GroundOverlay imageOverlay = map.addGroundOverlay(newarkMap);
// Update the GroundOverlay with a new image of the same dimensions.
imageOverlay = map.setImage(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1975));

The setImage() method will replace the existing image with another image of
the same dimensions.

Position a Ground Overlay

There are two ways to specify the position of the ground overlay:

Using a LatLng to center the overlay, and dimensions in meters to specify
the size of the image.

Using a LatLngBounds to specify the north east and south west corners of
the image.

You must specify the position of the ground overlay before it is added to the
map.

Use location to position an image

When you add the image you specify a LatLng to which the anchor will be fixed
and the width of the overlay (in meters). The
anchor defaults to the center of the
image. You can optionally provide the height of the overlay (in meters). If
you do not provide the height of the overlay, it will be automatically
calculated to preserve the proportions of the image.

The below code places an image at position 40.714086, -74.228697
that is 8.6km wide by 6.5km high. The image is anchored at the bottom left.

Use LatLngBounds to position an image

You provide a LatLngBounds which contains the image. The
LatLngBounds sets the north east, and south west corners of the image. When
the image is drawn on the map it will be rotated to fit the bounds. If the
bounds do not match the original aspect ratio, the image will be skewed.

The below code places an image on the map with its South West corner bound to
40.712216,-74.22655 and its North East corner bound to
40.773941, -74.12544.

LatLngBounds newarkBounds = new LatLngBounds(
new LatLng(40.712216, -74.22655), // South west corner
new LatLng(40.773941, -74.12544)); // North east corner
GroundOverlayOptions newarkMap = new GroundOverlayOptions()
.image(BitmapDescriptorFactory.fromResource(R.drawable.newark_nj_1922))
.positionFromBounds(newarkBounds);

Here are some examples of scenarios when it's useful to store and retrieve data
with ground overlays:

Your app may cater for different ground overlays, and you want to
treat them differently when the user clicks them.

You may be interfacing with a system that has unique record identifiers,
where the overlays represent specific records in that system.

The overlay data may indicate a priority to determine the z-index for the
overlay.

Handle ground overlay events

By default, ground overlays are
not clickable. You can enable and disable the clickability by calling
GroundOverlay.setClickable(boolean).

Use an OnGroundOverlayClickListener
to listen to click events on a clickable ground overlay. To set this listener on
the map, call
GoogleMap.setOnGroundOverlayClickListener(OnGroundOverlayClickListener).
When a user clicks on a ground overlay, you will receive an
onGroundOverlayClick(GroundOverlay) callback.

Note: If multiple overlays or shapes
(markers, polylines, polygons, circles and/or ground overlays) are overlaid on
top of each other, the click event is cycled through the cluster of markers
first, then triggered for other clickable overlays or shapes based on their
z-index values. At most one event is triggered per click. In other words, the
click is not passed down to the overlays or shapes with lower z-index values.
Read more about
marker z-index
and click events.